Fabrizio Bernardi - Academia.edu (original) (raw)
Papers by Fabrizio Bernardi
In our work we will discuss the conceptual design of an Expert Coordination Centre (ExpCen) suppo... more In our work we will discuss the conceptual design of an Expert Coordination Centre (ExpCen) supporting observations performed by optical and satellite laser ranging (SLR) sensors. This ExpCen should suit as an interface between a Space Surveillance and Tracking (SST) system, as example for technology developments under ESA’s SSA programme, and any external sensors. Presented will be identified ExpCen’s functionalities, such as coordination of sensors, validation and qualification of data and research and development. Presented will be high-level architecture of the centre along with the defined interfaces. ExpCen will perform several different tasks, each performed by different subsystem. The subsystems architecture, interfaces, data flows and components will be shown. The current design of the ExpCen allows to perform in parallel functionalities for optical passive and SLR domain.
Monthly Notices of the Royal Astronomical Society: Letters, 2008
Icarus, 2009
The potentially hazardous asteroid (101955) 1999 RQ 36 has a possibility of colliding with the Ea... more The potentially hazardous asteroid (101955) 1999 RQ 36 has a possibility of colliding with the Earth in the latter half of the 22nd century, well beyond the traditional 100-year time horizon for routine impact monitoring. The probabilities accumulate to a total impact probability of approximately 10 −3 , with a pair of closely related routes to impact in 2182 comprising more than half of the total. The analysis of impact possibilities so far in the future is strongly dependent on the action of the Yarkovsky effect, which raises new challenges in the careful assessment of longer term impact hazards. Even for asteroids with very precisely determined orbits, a future close approach to Earth can scatter the possible trajectories to the point that the problem becomes like that of a newly discovered asteroid with a weakly determined orbit. If the scattering takes place late enough so that the target plane uncertainty is dominated by Yarkovsky accelerations then the thermal properties of the asteroid, which are typically unknown, play a major role in the impact assessment. In contrast, if the strong planetary interaction takes place sooner, while the Yarkovsky dispersion is still relatively small compared to that derived from the measurements, then precise modeling of the nongravitational acceleration may be unnecessary.
Icarus, 2008
We present the first observational measurement of the orbit and size distribution of small solar ... more We present the first observational measurement of the orbit and size distribution of small solar system objects whose orbits are wholly interior to the Earth's. We show that we are able to model the detections of near-Earth objects (NEO) by the Catalina Sky Survey (CSS) using a detailed parameterization of the CSS survey cadence and detection efficiencies as implemented within the Jedicke et al. (2003) survey simulator and utilizing the Bottke et al. (2002) model of the NEO population's size and orbit distribution. We then show that the CSS detections of 4 objects that orbit the Sun entirely interior to the Earth's orbit (IEO, aphelion < 0.983 AU) are consistent with the Bottke et al. (2002) IEO model. Observational selection effects for the IEOs discovered by the CSS were then determined using the survey simulator in order to calculate the corrected number and H distribution of the IEOs. The actual number of IEOs with H < 18 (21) is 36 ± 26 (530 ± 240) and the slope of the H magnitude distribution (∝ 10 αH) for the IEOs is α IEO = 0.44 +0.23 −0.22. The slope is consistent with previous measurements for the NEO population of α N EO = 0.35 ± 0.02 (Bottke et al. 2002) and α N EO = 0.39 ± 0.013 (Stuart and Binzel 2004). Thus, there is no indication of any non-gravitational effects (e.g. Yarkovsky, tidal disruption) affecting the known IEO population based on the agreement between the predicted and observed IEO orbit and absolute magnitude distributions.
Celestial Mechanics and Dynamical Astronomy
Icarus, Oct 1, 2009
ABSTRACT The potentially hazardous Asteroid (101955) 1999 RQ has a possibility of colliding with ... more ABSTRACT The potentially hazardous Asteroid (101955) 1999 RQ has a possibility of colliding with the Earth in the latter half of the 22nd century, well beyond the traditional 100-year time horizon for routine impact monitoring. The probabilities accumulate to a total impact probability of approximately 10-3, with a pair of closely related routes to impact in 2182 comprising more than half of the total. The analysis of impact possibilities so far in the future is strongly dependent on the action of the Yarkovsky effect, which raises new challenges in the careful assessment of longer term impact hazards. Even for asteroids with very precisely determined orbits, a future close approach to Earth can scatter the possible trajectories to the point that the problem becomes like that of a newly discovered asteroid with a weakly determined orbit. If the scattering takes place late enough so that the target plane uncertainty is dominated by Yarkovsky accelerations then the thermal properties of the asteroid, which are typically unknown, play a major role in the impact assessment. In contrast, if the strong planetary interaction takes place sooner, while the Yarkovsky dispersion is still relatively small compared to that derived from the measurements, then precise modeling of the nongravitational acceleration may be unnecessary.
ABSTRACT In the framework of the European Space Agency - Space Situational Awareness (ESA-SSA) pr... more ABSTRACT In the framework of the European Space Agency - Space Situational Awareness (ESA-SSA) program, we studied the performance of a possible network of telescopes for the SSA Near Earth Objects (NEO) segment capable of scanning all the visible sky from a station in one single night (Wide Survey). The purpose of the study was the determination of the efficiency of discovering NEOs in the size range of the Tunguskalike asteroids, from 160 m down to 10 m. We developed an end-to-end simulator capable to simulate, under some assumptions, the activities of such a network from detection, to preliminary orbit determination, orbit improvement and impact risk assessment. This work presents the results of our simulations.
In the framework of the European Space Situational Awareness program, we considered a network of ... more In the framework of the European Space Situational Awareness program, we considered a network of telescopes capable of scanning all the observable sky each night, in order to determine the efficiency of discovering Near-Earth objects (NEOs) in the size range of the Tunguska-like asteroids, from 160 m down to 10 m. In the present paper we measure the performances of
We discuss a method to determine non gravitational parameters of asteroids. Non gravitational per... more We discuss a method to determine non gravitational parameters of asteroids. Non gravitational perturbations can lead to secular effects, thus changing the dynamical evolution. Moreover, the probability of an impact between the Earth and an asteroid can significantly change. To succeed in our purpose, we add non gravitational parameters to the set of unknowns in the procedure of least squares orbital fit. This technique allow us to compute both nominal values and covariance matrices for these parameters, provided the observational arc is long enough. As a test, we apply this approach to the case of 1999RQ36.
Earth, Moon, and Planets, 2014
ABSTRACT In this work we summarize the initial results of a targeted effort of the ESA NEO Coordi... more ABSTRACT In this work we summarize the initial results of a targeted effort of the ESA NEO Coordination Centre to obtain additional observational data in order to eliminate or reduce the impact probability estimate of a subset of the known near-Earth objects representing the highest fraction of the total known impact risk, as measured by the Palermo Scale.
The Astrophysical Journal, 2011
Using a slitless spectroscopy method with (a) the 8.2 m Subaru telescope and its FOCAS Cassegrain... more Using a slitless spectroscopy method with (a) the 8.2 m Subaru telescope and its FOCAS Cassegrain spectrograph, and (b) the ESO Very Large Telescope (VLT) unit 1 (Antu) and its FORS2 Cassegrain spectrograph, we have detected 326 planetary nebulae (PNs) in the giant Virgo elliptical galaxy NGC 4649 (M 60), and we have measured their radial velocities. After rejecting some PNs more likely to belong to the companion galaxy NGC 4647, we have built a catalog with kinematic information for 298 PNs in M 60. Using these radial velocities we have investigated if they support the presence of a dark matter halo around M 60. The preliminary conclusion is that they do; based on an isotropic, twocomponent Hernquist model, we estimate the dark matter halo mass within 3R e to be 4×10 11 M ⊙ , which is almost one half of the total mass of about 10 12 M ⊙ within 3R e. This total mass is similar to that estimated from globular cluster, XMM-Newton and Chandra observations. The dark matter becomes dominant outside. More detailed dynamical modeling of the PN data is being published in a companion paper. We have also measured the m(5007) magnitudes of many of these PNs, and built a statistically complete sample of 218 PNs. The resulting PN luminosity function (PNLF) was used to estimate a distance modulus of 30.7±0.2 mag, equivalent to 14±1 Mpc. This confirms an earlier PNLF distance measurement, based on a much smaller sample. The PNLF distance modulus remains smaller than the surface brightness fluctuation (SBF) distance modulus by 0.4 mag. The reason is still unknown.
Planetary and Space Science, 2012
We present the results of a large scale simulation, reproducing the behavior of a data center for... more We present the results of a large scale simulation, reproducing the behavior of a data center for the build-up and maintenance of a complete catalog of space debris in the upper part of the low Earth orbits region (LEO). The purpose is to determine the performances of a network of advanced optical sensors, through the use of the newest orbit determination algorithms developed by the Department of Mathematics of Pisa (DM). Such a network has been proposed to ESA in the Space Situational Awareness (SSA) framework by Carlo Gavazzi Space SpA (CGS), Istituto Nazionale di Astrofisica (INAF), DM, and Istituto di Scienza e Tecnologie dell'Informazione (ISTI-CNR). The conclusion is that it is possible to use a network of optical sensors to build up a catalog containing more than 98% of the objects with perigee height between 1100 and 2000 km, which would be observable by a reference radar system selected as comparison. It is also possible to maintain such a catalog within the accuracy requirements motivated by collision avoidance, and to detect catastrophic fragmentation events. However, such results depend upon specific assumptions on the sensor and on the software technologies.
Meteoritics & Planetary Science, 2009
AbstractWe present results from an observing campaign of 25143 Itokawa performed with the 2.2 m ... more AbstractWe present results from an observing campaign of 25143 Itokawa performed with the 2.2 m telescope of the University of Hawai&amp;#x27;i between November 2000 and September 2001. The main goal of this paper is to determine the absolute magnitude H and the slope ...
Icarus, 2012
The discovery of new objects in modern wide-field asteroid and comet surveys can be enhanced by f... more The discovery of new objects in modern wide-field asteroid and comet surveys can be enhanced by first identifying observations belonging to known solar system objects. The assignation of new observations to a known object is an attribution problem that occurs when a least squares orbit already exists for the object but a separate fit is not possible to just the set of new observations. In this work we explore the strongly asymmetric attribution problem in which the existing least squares orbit is very well constrained and the new data are sparse. We describe an attribution algorithm that introduces new quality control metrics in the presence of strong biases in the astrometric residuals. The main biases arise from the stellar catalogs used in the reduction of asteroid observations and we show that a simple debiasing with measured regional catalog biases significantly improves the results. We tested the attribution algorithm using data from the PS1 survey that used the 2MASS star catalog for the astrometric reduction. We found small but statistically significant biases in the data of up to 0.1 arcsec that are relevant only when the observations reach the level of accuracy made possible by instruments like PS1. The false attribution rate was measured to be < 1/1, 000 with a simple additional condition that can reduce it to zero while the attribution efficiency is consistent with 100%.
Icarus, 2012
We consider a network of telescopes capable of scanning all the observable sky each night and tar... more We consider a network of telescopes capable of scanning all the observable sky each night and targeting Near-Earth objects (NEOs) in the size range of the Tunguska-like asteroids, from 160 m down to 10 m. We measure the performance of this telescope network in terms of the time needed to discover at least 50% of the impactors in the considered population with a warning time large enough to undertake proper mitigation actions. The warning times are described by a trimodal distribution and the telescope network has a 50% probability of discovering an impactor of the Tunguska class with at least one week of advance already in the first 10 yr of operations of the survey. These results suggest that the studied survey would be a significant addition to the current NEO discovery efforts.
In the last years, scientific and technological goals pushed space agencies to plan and launch sp... more In the last years, scientific and technological goals pushed space agencies to plan and launch space missions to Near Earth Objects (NEOs). In this respect, observational programs devoted to the study of the physical nature of NEOs are needed in support of such a future space mission. Starting from the classical definition of &amp;amp;amp;quot;accessibility&amp;amp;amp;quot; of a celestial body in terms
In our work we will discuss the conceptual design of an Expert Coordination Centre (ExpCen) suppo... more In our work we will discuss the conceptual design of an Expert Coordination Centre (ExpCen) supporting observations performed by optical and satellite laser ranging (SLR) sensors. This ExpCen should suit as an interface between a Space Surveillance and Tracking (SST) system, as example for technology developments under ESA’s SSA programme, and any external sensors. Presented will be identified ExpCen’s functionalities, such as coordination of sensors, validation and qualification of data and research and development. Presented will be high-level architecture of the centre along with the defined interfaces. ExpCen will perform several different tasks, each performed by different subsystem. The subsystems architecture, interfaces, data flows and components will be shown. The current design of the ExpCen allows to perform in parallel functionalities for optical passive and SLR domain.
Monthly Notices of the Royal Astronomical Society: Letters, 2008
Icarus, 2009
The potentially hazardous asteroid (101955) 1999 RQ 36 has a possibility of colliding with the Ea... more The potentially hazardous asteroid (101955) 1999 RQ 36 has a possibility of colliding with the Earth in the latter half of the 22nd century, well beyond the traditional 100-year time horizon for routine impact monitoring. The probabilities accumulate to a total impact probability of approximately 10 −3 , with a pair of closely related routes to impact in 2182 comprising more than half of the total. The analysis of impact possibilities so far in the future is strongly dependent on the action of the Yarkovsky effect, which raises new challenges in the careful assessment of longer term impact hazards. Even for asteroids with very precisely determined orbits, a future close approach to Earth can scatter the possible trajectories to the point that the problem becomes like that of a newly discovered asteroid with a weakly determined orbit. If the scattering takes place late enough so that the target plane uncertainty is dominated by Yarkovsky accelerations then the thermal properties of the asteroid, which are typically unknown, play a major role in the impact assessment. In contrast, if the strong planetary interaction takes place sooner, while the Yarkovsky dispersion is still relatively small compared to that derived from the measurements, then precise modeling of the nongravitational acceleration may be unnecessary.
Icarus, 2008
We present the first observational measurement of the orbit and size distribution of small solar ... more We present the first observational measurement of the orbit and size distribution of small solar system objects whose orbits are wholly interior to the Earth's. We show that we are able to model the detections of near-Earth objects (NEO) by the Catalina Sky Survey (CSS) using a detailed parameterization of the CSS survey cadence and detection efficiencies as implemented within the Jedicke et al. (2003) survey simulator and utilizing the Bottke et al. (2002) model of the NEO population's size and orbit distribution. We then show that the CSS detections of 4 objects that orbit the Sun entirely interior to the Earth's orbit (IEO, aphelion < 0.983 AU) are consistent with the Bottke et al. (2002) IEO model. Observational selection effects for the IEOs discovered by the CSS were then determined using the survey simulator in order to calculate the corrected number and H distribution of the IEOs. The actual number of IEOs with H < 18 (21) is 36 ± 26 (530 ± 240) and the slope of the H magnitude distribution (∝ 10 αH) for the IEOs is α IEO = 0.44 +0.23 −0.22. The slope is consistent with previous measurements for the NEO population of α N EO = 0.35 ± 0.02 (Bottke et al. 2002) and α N EO = 0.39 ± 0.013 (Stuart and Binzel 2004). Thus, there is no indication of any non-gravitational effects (e.g. Yarkovsky, tidal disruption) affecting the known IEO population based on the agreement between the predicted and observed IEO orbit and absolute magnitude distributions.
Celestial Mechanics and Dynamical Astronomy
Icarus, Oct 1, 2009
ABSTRACT The potentially hazardous Asteroid (101955) 1999 RQ has a possibility of colliding with ... more ABSTRACT The potentially hazardous Asteroid (101955) 1999 RQ has a possibility of colliding with the Earth in the latter half of the 22nd century, well beyond the traditional 100-year time horizon for routine impact monitoring. The probabilities accumulate to a total impact probability of approximately 10-3, with a pair of closely related routes to impact in 2182 comprising more than half of the total. The analysis of impact possibilities so far in the future is strongly dependent on the action of the Yarkovsky effect, which raises new challenges in the careful assessment of longer term impact hazards. Even for asteroids with very precisely determined orbits, a future close approach to Earth can scatter the possible trajectories to the point that the problem becomes like that of a newly discovered asteroid with a weakly determined orbit. If the scattering takes place late enough so that the target plane uncertainty is dominated by Yarkovsky accelerations then the thermal properties of the asteroid, which are typically unknown, play a major role in the impact assessment. In contrast, if the strong planetary interaction takes place sooner, while the Yarkovsky dispersion is still relatively small compared to that derived from the measurements, then precise modeling of the nongravitational acceleration may be unnecessary.
ABSTRACT In the framework of the European Space Agency - Space Situational Awareness (ESA-SSA) pr... more ABSTRACT In the framework of the European Space Agency - Space Situational Awareness (ESA-SSA) program, we studied the performance of a possible network of telescopes for the SSA Near Earth Objects (NEO) segment capable of scanning all the visible sky from a station in one single night (Wide Survey). The purpose of the study was the determination of the efficiency of discovering NEOs in the size range of the Tunguskalike asteroids, from 160 m down to 10 m. We developed an end-to-end simulator capable to simulate, under some assumptions, the activities of such a network from detection, to preliminary orbit determination, orbit improvement and impact risk assessment. This work presents the results of our simulations.
In the framework of the European Space Situational Awareness program, we considered a network of ... more In the framework of the European Space Situational Awareness program, we considered a network of telescopes capable of scanning all the observable sky each night, in order to determine the efficiency of discovering Near-Earth objects (NEOs) in the size range of the Tunguska-like asteroids, from 160 m down to 10 m. In the present paper we measure the performances of
We discuss a method to determine non gravitational parameters of asteroids. Non gravitational per... more We discuss a method to determine non gravitational parameters of asteroids. Non gravitational perturbations can lead to secular effects, thus changing the dynamical evolution. Moreover, the probability of an impact between the Earth and an asteroid can significantly change. To succeed in our purpose, we add non gravitational parameters to the set of unknowns in the procedure of least squares orbital fit. This technique allow us to compute both nominal values and covariance matrices for these parameters, provided the observational arc is long enough. As a test, we apply this approach to the case of 1999RQ36.
Earth, Moon, and Planets, 2014
ABSTRACT In this work we summarize the initial results of a targeted effort of the ESA NEO Coordi... more ABSTRACT In this work we summarize the initial results of a targeted effort of the ESA NEO Coordination Centre to obtain additional observational data in order to eliminate or reduce the impact probability estimate of a subset of the known near-Earth objects representing the highest fraction of the total known impact risk, as measured by the Palermo Scale.
The Astrophysical Journal, 2011
Using a slitless spectroscopy method with (a) the 8.2 m Subaru telescope and its FOCAS Cassegrain... more Using a slitless spectroscopy method with (a) the 8.2 m Subaru telescope and its FOCAS Cassegrain spectrograph, and (b) the ESO Very Large Telescope (VLT) unit 1 (Antu) and its FORS2 Cassegrain spectrograph, we have detected 326 planetary nebulae (PNs) in the giant Virgo elliptical galaxy NGC 4649 (M 60), and we have measured their radial velocities. After rejecting some PNs more likely to belong to the companion galaxy NGC 4647, we have built a catalog with kinematic information for 298 PNs in M 60. Using these radial velocities we have investigated if they support the presence of a dark matter halo around M 60. The preliminary conclusion is that they do; based on an isotropic, twocomponent Hernquist model, we estimate the dark matter halo mass within 3R e to be 4×10 11 M ⊙ , which is almost one half of the total mass of about 10 12 M ⊙ within 3R e. This total mass is similar to that estimated from globular cluster, XMM-Newton and Chandra observations. The dark matter becomes dominant outside. More detailed dynamical modeling of the PN data is being published in a companion paper. We have also measured the m(5007) magnitudes of many of these PNs, and built a statistically complete sample of 218 PNs. The resulting PN luminosity function (PNLF) was used to estimate a distance modulus of 30.7±0.2 mag, equivalent to 14±1 Mpc. This confirms an earlier PNLF distance measurement, based on a much smaller sample. The PNLF distance modulus remains smaller than the surface brightness fluctuation (SBF) distance modulus by 0.4 mag. The reason is still unknown.
Planetary and Space Science, 2012
We present the results of a large scale simulation, reproducing the behavior of a data center for... more We present the results of a large scale simulation, reproducing the behavior of a data center for the build-up and maintenance of a complete catalog of space debris in the upper part of the low Earth orbits region (LEO). The purpose is to determine the performances of a network of advanced optical sensors, through the use of the newest orbit determination algorithms developed by the Department of Mathematics of Pisa (DM). Such a network has been proposed to ESA in the Space Situational Awareness (SSA) framework by Carlo Gavazzi Space SpA (CGS), Istituto Nazionale di Astrofisica (INAF), DM, and Istituto di Scienza e Tecnologie dell'Informazione (ISTI-CNR). The conclusion is that it is possible to use a network of optical sensors to build up a catalog containing more than 98% of the objects with perigee height between 1100 and 2000 km, which would be observable by a reference radar system selected as comparison. It is also possible to maintain such a catalog within the accuracy requirements motivated by collision avoidance, and to detect catastrophic fragmentation events. However, such results depend upon specific assumptions on the sensor and on the software technologies.
Meteoritics & Planetary Science, 2009
AbstractWe present results from an observing campaign of 25143 Itokawa performed with the 2.2 m ... more AbstractWe present results from an observing campaign of 25143 Itokawa performed with the 2.2 m telescope of the University of Hawai&amp;#x27;i between November 2000 and September 2001. The main goal of this paper is to determine the absolute magnitude H and the slope ...
Icarus, 2012
The discovery of new objects in modern wide-field asteroid and comet surveys can be enhanced by f... more The discovery of new objects in modern wide-field asteroid and comet surveys can be enhanced by first identifying observations belonging to known solar system objects. The assignation of new observations to a known object is an attribution problem that occurs when a least squares orbit already exists for the object but a separate fit is not possible to just the set of new observations. In this work we explore the strongly asymmetric attribution problem in which the existing least squares orbit is very well constrained and the new data are sparse. We describe an attribution algorithm that introduces new quality control metrics in the presence of strong biases in the astrometric residuals. The main biases arise from the stellar catalogs used in the reduction of asteroid observations and we show that a simple debiasing with measured regional catalog biases significantly improves the results. We tested the attribution algorithm using data from the PS1 survey that used the 2MASS star catalog for the astrometric reduction. We found small but statistically significant biases in the data of up to 0.1 arcsec that are relevant only when the observations reach the level of accuracy made possible by instruments like PS1. The false attribution rate was measured to be < 1/1, 000 with a simple additional condition that can reduce it to zero while the attribution efficiency is consistent with 100%.
Icarus, 2012
We consider a network of telescopes capable of scanning all the observable sky each night and tar... more We consider a network of telescopes capable of scanning all the observable sky each night and targeting Near-Earth objects (NEOs) in the size range of the Tunguska-like asteroids, from 160 m down to 10 m. We measure the performance of this telescope network in terms of the time needed to discover at least 50% of the impactors in the considered population with a warning time large enough to undertake proper mitigation actions. The warning times are described by a trimodal distribution and the telescope network has a 50% probability of discovering an impactor of the Tunguska class with at least one week of advance already in the first 10 yr of operations of the survey. These results suggest that the studied survey would be a significant addition to the current NEO discovery efforts.
In the last years, scientific and technological goals pushed space agencies to plan and launch sp... more In the last years, scientific and technological goals pushed space agencies to plan and launch space missions to Near Earth Objects (NEOs). In this respect, observational programs devoted to the study of the physical nature of NEOs are needed in support of such a future space mission. Starting from the classical definition of &amp;amp;amp;quot;accessibility&amp;amp;amp;quot; of a celestial body in terms